<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9">
    <title>dygraphs Equation Plotter</title>
    <!--[if IE]>
    <script type="text/javascript" src="../excanvas.js"></script>
    <![endif]-->
    <!--
    For production (minified) code, use:
    <script type="text/javascript" src="dygraph-combined.js"></script>
    -->
    <script type="text/javascript" src="../dygraph-dev.js"></script>

    <script type="text/javascript">
      function plot() {
        var eq = document.getElementById("eq").value;
        eval("fn = " + eq);

        var graph = document.getElementById("graph_div");
        var width = parseInt(graph.style.width);
        var x1 = parseFloat(document.getElementById("x1").value);
        var x2 = parseFloat(document.getElementById("x2").value);
        var xs = 1.0 * (x2 - x1) / width;

        var data = [];
        for (var i = 0; i < width; i++) {
          var x = x1 + i * xs;
          var y = fn(x);
          var row = [x];
          if (y.length > 0) {
            for (var j = 0; j < y.length; j++) {
              row.push(y[j]);
            }
          } else {
            row.push(y);
          }
          data.push(row);
        }

        var labels = ['X'];
        if (data[0].length == 2) {
          labels.push('Y');
        } else {
          for (var i = 1; i < data[0].length; i++) {
            labels.push('Y' + (1 + i));
          }
        }

        g = new Dygraph(graph, data, {
          labels: labels
        });
      }

      function preset() {
        var sel = document.getElementById("presets").selectedIndex;
        var id = document.getElementById("presets").options[sel].id;
        var presets = {
          'id': [ -10, 10, 'function(x) {\n  return x;\n}' ],
          'sine': [ -10, 10, 'function(x) {\n  return Math.sin(x);\n}' ],
          'taylor': [ -3, 3, 'function(x) {\n  return [Math.cos(x), 1 - x*x/2 + x*x*x*x/24];\n}' ],
          'sawtooth': [-10, 10, 'function(x) {\n  var y = 0;\n  for (var i = 1; i < 20; i+=2) {\n    y += Math.sin(i * x)/i;\n  }\n  var final = 1 - 2*(Math.abs(Math.floor(x / Math.PI)) % 2);\n  return [4/Math.PI * y, final];\n}' ]
        };

        if (id == "custom") { return; }
        document.getElementById("x1").value = presets[id][0];
        document.getElementById("x2").value = presets[id][1];
        document.getElementById("eq").value = presets[id][2];
        plot();
      }
    </script>
  </head>
  <body onload="preset()">
    <p><b>Equation: </b><br/>
    <textarea cols="40" rows="10" id="eq">function(x) {
  return [0.1 * x, 0.1 * x + Math.sin(x), 0.1*x + Math.cos(x)];
}</textarea><br/>
<b>Preset functions:</b> <select id=presets onchange="preset()">
<option id=custom>(custom)</option>
<option id=id>Identity</option>
<option id=sine>Sine Wave</option>
<option id=taylor>Taylor series</option>
<option selected id=sawtooth>Sawtooth</option>
</select>
    </p>

    <p><b>x range: </b> <input type=text width="5" id="x1" value="-10" />
    to <input type=text width="5" id="x2" value="10" /></p>
    <p><input type=button value="Plot" onClick="plot()" /></p>

    <div id="graph_div" style="width:1024px; height:400px;"></div>
  </body>
</html>
